The present invention relates to forging presses and more particularly relates to a table shift apparatus for large hydraulic presses.
The present application is related to the general subject matter described in patent application Ser. No. 821,790 A Forging Press with Adjustable Daylight and with Yoke Design for Attaching Tierods to Crossheads which is commonly assigned with the present application. The subject matter thereof is incorporated herein by reference.
Forging presses as is well known are used for shaping metal slabs or ingots into end products of desired shape by pressing the metal slab between a pair of dies to give it its shape. To this end the forging press comes equipped with a working table of considerable dimensions which table is loaded with dies and bolsters and the unshaped metal slab. A table of this type can measure 30 feet in length and weigh close to 1,000 tons.
At times it is necessary to shift the table in and out from under the press at a considerable speed for heavy components of this type. Speeds of 700-800 inches per minute over distances of 100 feet are contemplated.
In prior art devices movement of the working table is effected by an actuator, usually of the water or oil hydraulic type which is capable of developing an operating force of 300 tons or more and which consists of one or more hydraulic cylinders and rams which pull the working table from under the press and then push it back into place.
Pulling the heavy working table is not difficult because the rams of the hydraulic cylinders work in tension only. Consequently, the table can be moved out from under the press at considerable speed. On the other hand, during pushing operations the long cylinder rams are in compression and thus susceptible to buckling. As a result it has been customary to complete the pushing operation in two stages and at a slower pace. This prior art arrangement adversely affects both the overall efficiency of the forging press and the size and capacity ratings of the hydraulic cylinders required for moving the working table.